to be more specific - you will see additional charges fromyour cell provider, but not on the cruise ship directly.
Your cell provider sees your phone as being in a roaming area - actually two at the same time. First it sees you are someplace overseas, so that is one roaming area (out of the U.S.) - then it sees you are using satelitle bandwidth (because you are at sea) and that is an additional charge.
For what it is worth - Blackberry is still the most reasonably priced cell service for overseas use. The iPhone is prohibitive.
If you want to save some money just turn it on when you are in port.
As I recall, a one-week cruise would usually add up to about $50 extra just for email on my Blackberry (I don't go that route anymore - I just use my laptop).
Susan I have an Iphone and when I go international for business I put my iphone in airplane mode. This shuts down the phone and data; I then turn on my wifi, which allows me to receive email in hotels. Most hotels overseas offer free wifi in the lobby. U should be able to do the same thing with your blackberry; keep it in airplane mode on ship; when u get to port turn on wifi; there are free wifi hotspots in port so u can check email then; or just leave it off the entire trip and have fun.
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